Conventionally, in the manufacturing of semiconductor devices, fine processing using a photolithography technology has been performed. The fine processing is a processing method including: forming a thin film of a photoresist composition on a substrate to be processed, such as silicon wafer; irradiating an activating light ray, such as ultra violet rays, onto the resultant thin film through a mask pattern in which a pattern of a semiconductor device is depicted to develop the pattern; and subjecting the substrate to be processed, such as silicon wafer, to etching processing using the resultant photoresist pattern as a protecting film. Recently, the high integration of semiconductor devices has been progressed and the activating light ray to be used has a shorter wavelength, from a KrF excimer laser (248 nm) to an ArF excimer laser (193 nm). Following such a tendency, the influence of diffuse reflection of an activating light ray from the substrate or of a standing wave has become a large problem. A method of providing a bottom anti-reflective coating (BARC) between the photoresist and the substrate to be processed as a resist underlayer film assuming a role of preventing reflection, has been widely adopted.
As such a bottom anti-reflective coating, there are known inorganic bottom anti-reflective coatings such as films of titanium, titanium dioxide, titanium nitride, chromium oxide, carbon, and α-silicon, and organic bottom anti-reflective coatings containing a light-absorptive substance and a polymer compound. The former requires in a film-forming process, equipment such as a vacuum evaporator, a CVD apparatus and a sputtering apparatus, while the latter requires no special equipment. Therefore, the latter is regarded as more advantageous, and many investigations thereon are carried out.
Examples of the organic bottom anti-reflective coatings include: an acrylic resin-based bottom anti-reflective coating having both a hydroxyl group which is a crosslinking reactive group and a light absorbing group within one molecule (see Patent Document 1); and a novolak resin-based bottom anti-reflective coating having both a hydroxyl group which is a crosslinking reactive group and a light absorbing group within one molecule (see Patent Document 2).
As physical properties desired for the organic bottom anti-reflective coating material, there are described: having a large absorbance relative to light or radiation; causing no intermixing with a photoresist layer (being insoluble in a resist solvent); causing no diffusion of low molecule substances from the bottom anti-reflective coating material to the inside of the overcoat resist during application or drying by heating; having a larger dry etching rate than that of the photoresist; and the like (see Non-patent Document 1).
Recently, as a next-generation photolithography technology succeeding the photolithography technology that uses an ArF excimer laser (193 nm), there is vigorously studied an ArF immersion lithography technology in which exposure is performed through water. However, the photolithography technology using light is reaching the limit, and as a new lithography technology after the ArF immersion lithography technology, an electron beam lithography technology using an electron beam has been receiving attention.
In a device production process using electron beam lithography, due to adverse effects caused by a base substrate or an electron beam, the pattern of a resist for electron beam lithography becomes in a trailing shape or an undercut shape, so that there are caused such problems that a favorable resist pattern in a straight shape cannot be formed and that a satisfactory margin relative to an electron beam irradiance level cannot be obtained. Therefore, in an electron beam lithography process, a resist underlayer film (bottom anti-reflective coating) having a reflection preventing function is unnecessary. However, there becomes necessary a resist underlayer film for electron beam lithography capable of obtaining a satisfactory margin relative to an electron beam irradiance level by reducing the above adverse effects to form a favorable resist pattern in a straight shape.
In addition, since a resist is applied on the resist underlayer film for electron beam lithography after the resist underlayer film is formed, it is essential characteristics of the resist underlayer film for electron beam lithography to cause no intermixing with the resist layer (being insoluble in a resist solvent) and to cause no diffusion of low molecule substances from a bottom anti-reflective coating material to the inside of the overcoat resist while applying or heating-drying.
Furthermore, in a generation using electron beam lithography, a resist pattern width becomes extremely fine, so that a resist for electron beam lithography is desired to be thinned. Therefore, it is necessary to significantly reduce the time for a process of removing an organic bottom anti-reflective coating by etching and there is required a resist underlayer film for electron beam lithography capable of being used in a thin film form or a resist underlayer film for electron beam lithography having a large selection ratio of an etching rate relative to a resist for electron beam lithography.